Problem: Simplify the following expression: $p = \dfrac{-3x - 21}{3x}$ You can assume $x \neq 0$.
Find the greatest common factor of the numerator and denominator. The numerator can be factored: $-3x - 21 = - (3 \cdot x) - (3\cdot7)$ The denominator can be factored: $3x = (3 \cdot x)$ The greatest common factor of all the terms is $3$ Factoring out $3$ gives us: $p = \dfrac{(3)(-x - 7)}{(3)(x)}$ Dividing both the numerator and denominator by $3$ gives: $p = \dfrac{-x - 7}{x}$